Deletions with lower BSC numbers were generated by the Hybrid Element Insertion (HEI) method described in Parks et al., 2004 (exceptions noted below) and are not isogenic. These deletions were induced by P-element transposase in the presence of trans-heterozygous P-element insertions. The HEI model predicts that one deletion endpoint will correspond to the insertion site of one of the starting insertions and the other endpoint will map near the other insertion site. The precise endpoints have not been characterized molecularly. Df(3L)BSC1, Df(3L)BSC2 and Df(2L)BSC7 were generated by irradiation mutagenesis and are not isogenic. Their breakpoints have been characterized cytologically, but not molecularly.